The opened page is the Power Query Editor, where the transformation of data takes place before it's loaded.
Stated below are the outlined steps and the GIF:
Filtering out some years at the Power Query Editor:
There was inconsistency in the data. 2004 was missing, so I had to remove all the data before 2005 to report something meaningful.
At the Power Query Editor, select Survey Year and click on the drop-down arrow at the corner.
A dialogue box opens up; click on sort Ascending.
Click to unselect all the years before 2005, click on Load more, and Ok.
6. Replace values:
a. Go to the Replace Values tab at the Power Query Editor
b. In the opened dialog box, put in the value to replace and what to be replaced with, as shown below:
c. Do this for the 6 survey questions.
Find below screenshots of the replaced Survey Questions and 'NULL' replaced with 'zero.'
7. Renamed Columns; Demographics_Question, Demographics_Response, and Survey Question.
Click on the Demographics_Question column
Right-click on the column name and select the rename column.
Repeat it for the other 2 columns.
8. Click on Close and Apply
Click on the link below for a better understanding of working in Power BI Power Query Editor.
https://docs.microsoft.com/en-us/power-query/power-query-quickstart-using-power-bi